Aluminum Syntactic Foam Research Articles

Experimental and numerical analysis of the compression behavior of aluminum syntactic foams reinforced with alumina hollow particles

In this study, analytical, numerical, and experimental methods are used to investigate the compressive behavior of alumina hollow particles reinforced aluminum matrix syntactic foams (AMSF). The representative volume element (RVE) models are generated for different volume fractions to analyze the elastic and elastio-plastic behavior of AMSFs using the FE solver ABAQUS. The geometric feature of the hollow particles is selected close to the actual physical dimensions. The effective elastic properties are estimated using linear homogenization models. For example, the elastic properties predicted using the Mori-Tanaka model are close to the FE-based RVE model data. Later, the macroscopic response (stress-strain data) is determined using the volume-averaging method proposed in the literature. The stress-strain response of the FE model with a 30% volume fraction has shown close agreement with the experimental data. Further, a parametric study is conducted for different particle wall thicknesses. These FE models have great potential in studying the ceramic hollow particles reinforced metal matrix syntactic foams and developing new porous composites under compression loading using RVE-based models.

Quasi-static compressive response and energy absorption properties of aluminum matrix syntactic foams: Room temperature and elevated temperature conditions

Aluminum matrix syntactic foams(AMSF) are lightweight composite foams with functional and structural properties such as low relative density and high energy absorbing nature. These qualities made AMSFs a practical alternative to conventional materials desirable for automotive, aerospace and shipbuilding industries as energy absorbers. Many studies have reported the mechanical aspects of these materials. However, a detailed analysis of energy-absorbing behavior on aluminum matrix syntactic foams is sparse. This work produces alumina-reinforced aluminum syntactic foams using the powder metallurgy route. A systematic study on quasi-static room temperature (RT) and elevated temperature (ET) is conducted to understand the effect of the volume fraction and size of the particle individually. The compressive stress-strain response shows volume fraction and temperature dependency for different particle size ranges. The maximum densification strain (RT-58% and ET- 55%) and energy absorption efficiency (RT- 70.61% and ET-75.77%) of samples tested in quasi-static- RT and ETs are observed, respectively. Despite large deformation, no sudden drop in stress-strain response and macroscopic stability were observed in the samples.

Numerical Analysis of Double-Leaf Composite Stiffened Door Subjected to Blast Loading

Doors are the most critical part in any structure as they may eventually fail first when subjected to extreme loads such as blasts. Blast resistant doors in a structure work as effective barriers against blast pressure thus making the entire structure safe. Accordingly, the need to provide blast resistant doors arises in important structures to endure blast pressure. Herein, the comparative performance of a three-hinged five-latched double leaf composite door subjected to blast loading is investigated using finite element analysis software LsDyna. The composite door consists of front and rear steel plates composed of armor steel and three different infill materials, i.e., polyurethane (PU) foam, aluminum syntactic foam with 200 μm cenosphere (Al200), or plain cement concrete (PC) are explored in this investigation. Comparative studies of these composite doors are performed by varying the thicknesses and types of infill material and blast-scaled distances. The peak deflection, permanent deflection, internal energy, and total energy are compared among the doors considered herein. Weight and cost analysis of the door are also considered to determine the most cost-effective solution. The numerical results show that the polyurethane core door illustrates better performance for 150 mm of core material. However, the plain concrete infill door and cenosphere aluminum alloy core door demonstrate enhanced performance for 100 mm core thickness at 0.15, 0.2, 0.3, and 0.4 m/kg1/3 scaled distances.

Preparation and quasi-static compression properties of hybrid aluminum matrix syntactic foam reinforced with glass cenospheres and silicon carbide nanowires

Conventional hybrid aluminum matrix syntactic foam with various hollow fillers shows low density and high densification strain. However, its peak stress can hardly be increased, resulting in a limited improvement in the energy absorption capacity. Although composites can be reinforced by adding ceramic nanoparticles, it is difficult to achieve dispersion of both hollow and dense fillers in the metal matrix due to their distinct density difference. In this study, we use silicon carbide nanowires reinforced aluminum swarf as the source of ceramic fillers, and prepare hybrid aluminum syntactic foam reinforced by both glass cenospheres and silicon carbide nanowires. The resulting syntactic foam shows low density of 1.3 g cm −3 , high peak stress of 128.6 MPa, and high energy absorption capacity of 60.70 MJ m −3 . Moreover, we demonstrate a novel way to recycle silicon carbide reinforced aluminum composites for reprocessing. • HASF reinforced with a hollow and a dense nanowire filler. • Glass cenospheres and SiCnw forming high dispersion of microscale domains in HASF. • Reprocessing both metal matrix and SiCnw fillers at the same time. • HASF showing strength of 128.6 MPa and energy absorption capacity of 60.70 MJ m −3 .

New Aluminum Syntactic Foam: Synthesis and Mechanical Characterization.

Metal matrix syntactic foams (MMSF) are advanced cellular materials constituted by a system of a minimum of two phases, in which a dispersion of hollow particles is embedded by a continuous metal matrix. The incorporation of porous fillers favors the development of low-density materials with exceptional behavior for damping vibrations, impacts, and blast effects, shielding acoustic, thermal, and electromagnetic energies. There are three main techniques to produce them: infiltration casting technique (ICT), stir casting technique (SCT), and powder metallurgy technique (P/M). The first two techniques are used for embedding filler into lower melting point metallic matrices than fillers, in contrast to P/M. The present study demonstrates the feasibility of producing MMSF with components of similar melting points by ICT. The fillers were synthesized in-situ with aluminum and a natural foaming agent from wastes of Spanish white marble quarries. These novel aluminum syntactic foams (ASF) were mechanically characterized following the ISO-13314 and exhibited a porosity, plateau stress, and energy absorption capacity of 41%, 37.65 MPa, 8.62 MJ/m3 (at 35% of densification), respectively. These properties are slightly superior to equal porosity LECA ASF, making these novel ASF suitable for the same applications as LECA-ASF.

Influences of reinforcement size and artificial aging on the compression features of hybrid ceramic filled aluminum syntactic foams

Over the past years, the number of scientific efforts on aluminum matrix syntactic foams (AMSFs) has increased in a noteworthy manner, and different investigation teams have tried to figure out the physical, microstructural, and mechanical properties of AMSFs. In this paper, different from the previous valuable efforts, an industrial-focused cold chamber die casting machine was utilized during the fabrication instead of commonly used lab-scale techniques. Also, the effects of the reinforcement diameter on the compressive features were analyzed for pumice and expanded glass-added hybrid AMSFs. To ascertain the mechanical properties, quasi-static compression tests were conducted and stress–strain curves were obtained. During the compression tests, the deformation styles of the hybrid foams were followed to comprehend their damage mechanisms. Moreover, half of the samples were subjected to artificial aging treatment and the results were checked up with as-cast samples. According to experimental outcomes, it was obvious that the artificial aging treatment caused superior mechanical properties and triggered brittle-style deformation.

Mechanical and Physical Characteristics of Bubble Alumina Reinforced Aluminum Syntactic Foams Made Through Recyclable Pressure Infiltration Technique

Metal matrix syntactic foams (MMSFs) are advance hybrid materials which reflect synergetic combination of particle reinforced composites and close cell metal foams. Recently, MMSFs have become considerably popular for several industrial areas because of their low density, high compression strength, good ductility and perfect energy absorption ability. In this paper, Al 7075/bubble alumina syntactic foams were fabricated by recyclable pressure infiltration casting method. Macroscopic and microscopic investigations showed that almost flawless infiltration was obtained between 2 – 4 mm hollow bubble alumina spheres and total porosity values of fabricated foams varied between % 43.2 and % 45.6. As for mechanical analyses, all foam samples were subjected to quasi-static compression test (1 mm/min deformation rate) and their crucial properties such as compression strength, plateau strength, densification strain and energy absorption capacity were determined. Besides, aging heat treatment (T6) was applied to certain samples in order to explore probable effects of heat treatment on the mechanical responses. The outcomes indicated that there was a positive relationship between the aging treatment and compressive features. Under the compressive loading, even though T6 treated foams showed a tendency to brittle fracture, their as-cast variants exhibited ductile behavior.

Effects of particle size, bimodality and heat treatment on mechanical properties of pumice reinforced aluminum syntactic foams produced by cold chamber die casting

In recent years, metal matrix syntactic foams (MMSFs) have become highly attractive owing to their unique physical, microstructural and mechanical features. Due to their promising potential for different industrial areas like automotive, aviation, and defense, these advanced engineering materials can also be evaluated as serious alternatives to particle reinforced metallic composites and conventional metallic foams. Differently from previously reported laboratory scaled techniques in the literature, this experimental effort focuses on the feasibility of MMSF manufacturing via a fully automated and industrial-based cold chamber die casting technique. Accordingly, 1–2 mm, 2–4 mm, and bimodal (50vol.%) natural-based pumice filled aluminum syntactic foams were manufactured utilizing a purpose-made casting machine. Physical, macroscopic, and microscopic examinations show that all of the fabricated samples display perfect matrix/filler harmony. Average density levels of fabricated syntactic foams range between 1.50 and 1.80 g·cm−3 depending upon the pumice particles size interval. To assess mechanical responses, quasi-static compression tests were performed. Furthermore, half of the foam samples were subjected to heat treatment to explore possible influences of aging on the compressive features and damage modes. Results indicate that although the heat treatment enhances the compressive strength, plateau stress, and energy absorption properties of the fabricated foams, it changes damage mode of the samples by causing brittle dominant deformation.

Effect of Aging Heat Treatment on Compressive Characteristics of Bimodal Aluminum Syntactic Foams Produced by Cold Chamber Die Casting

Effect of Aging Heat Treatment on Compressive Characteristics of Bimodal Aluminum Syntactic Foams Produced by Cold Chamber Die Casting

Synthesis and Characterization of Hollow Glass Sphere Containing Aluminum Syntactic Foam by Spark Plasma Sintering and Hot Pressing

The effect of sintering process on the microstructure and the mechanical properties of aluminum syntactic foam were investigated in this study. Two different sintering processes of spark plasma sintering and hot pressing were used. Glass hollow spheres with a size of 50–80 μm was used to fabricate the foams having various volume fractions of the spheres in the range of 10–30%. Microstructural analysis revealed that the glass hollow spheres were uniformly distributed in the aluminum matrix, both in the spark plasma sintered and hot pressed ones. As the volume fraction of the spheres increased from 10 to 30%, the density, micro-hardness and compressive strength of the foams were decreased. In comparison to the foams fabricated by hot pressing method, the spark plasma sintered foams had slightly lower density and mechanical strength. In nanoindentation study, it was found that the aluminum matrix in the foam prepared by the spark plasma sintering process had lower strength than foam prepared by the hot pressing process. This is likely because of shorter sintering time used in the spark plasma sintering process than the hot pressing.

Microstructural characterization and compression mechanical response of glass hollow spheres/Al syntactic foams with different Mg additions

Aluminum syntactic foams with different magnesium contents were fabricated by pressure infiltration of glass hollow spheres. Effect of Mg addition on microstructure, compression properties and corresponding deformation behavior as well as energy absorption under different strain rates loading was experimental investigated. Increasing Mg contents resulted in interface reactions between matrix and glass spheres forming MgAl2O4, Si and Mg2Si hard phases, leading to the improvement of compression strength, structural stiffness and energy absorption capacity of syntactic foams, however, reducing the strain rate sensitivity of the syntactic foams. The addition of Mg content decreased the stress relaxation and load transfer ability of the matrix and developed the syntactic foam into severe brittle fracture during quasi-static compression. Nevertheless, the influence of Mg addition on the macroscopic compression deformation behavior of syntactic foams was weakened at increasing high strain rate loading.

Vulnerability analysis of tunnel linings under blast loading

In the present study, a comparative assessment on the performance of conventional and advanced tunnel lining materials subjected to blast loading is done using a three-dimensional non-linear finite element analysis procedure. The conventional tunnel lining materials analyzed herein are plain concrete, steel, reinforced cement concrete, and steel fiber–reinforced concrete. The advanced tunnel lining materials analyzed herein are dytherm, polyurethane, and aluminum syntactic foam sandwich panels with steel–foam–steel composites. The pressure generated by 10 kg Trinitrotoluene (TNT) is applied to each element on the inner wall of the tunnel which has an effect equal to the scaled distance Z = 1.16 m/kg1/3. Analyses are conducted by varying the thickness of lining materials for a tunnel built in rock domain. The response of the tunnel lining materials, for example, deformation, stresses, and strains generated at different interfaces, is compared with each other to assess the best suitable material for the present blast scenario discussed herein. It is observed from the simulations that the reinforced cement concrete and steel–aluminum syntactic foam (90 µm)–steel are found to be the suitable tunnel lining materials for the present blasting scenario described herein. Moreover, a set of probabilistic analysis is also performed for the suitable tunnel lining materials decided through deterministic analyses using Monte Carlo simulations. The results obtained are normal random distribution curves depicting the extent of deformation in lining materials. A probability failure curve is also proposed for the suitable lining materials.

Preparation and Properties of C/C Hollow Spheres and the Energy Absorption Capacity of the Corresponding Aluminum Syntactic Foams.

The present study focuses on the preparation and characterization of lab-scale aluminum syntactic foams (ASFs) filled with hollow carbon spheres (HCSs). A new and original process for the fabrication of HCSs was explored. Firstly, expanded polystyrene beads with an average diameter of 6 mm and coated with carbon fibers/thermoset phenolic resin were produced by the “rolling ball” method. In the next step, the spheres were cured and post-cured, and then carbonized at 1050 °C under vacuum to form the HCSs. The porosity in the shell of the HCSs was decreased by increasing the number of impregnation–carbonization cycles. The aluminum syntactic foams were fabricated by casting the molten aluminum into a crucible filled with HCSs. The morphology of the hollow spheres before and after carbonization was investigated by scanning electron microscope (SEM). The compressive properties of the ASF were tested and the energy absorption capacities were calculated according to stress–strain curves. The results showed that the ASF filled with HCSs which had been treated by more cycles of impregnation–carbonization had higher energy absorption capacity. The aluminum syntactic foam absorbed 34.9 MJ/m3 (28.8 KJ/Kg) at 60% strain, which was much higher than traditional closed cell aluminum foams without particles. The HCSs have a promising future in producing a novel family of metal matrix syntactic foams.

Comparative Study on Microstructural Characteristics and Compression Deformation Behaviour of Alumina and Cenosphere Reinforced Aluminum Syntactic Foam Made Through Stir Casting Technique

In order to examine the effect of microballoons type on microstructure and compressive deformation behaviour of aluminum syntactic foam, alumina reinforced and cenosphere reinforced aluminum syntactic foams have been made through stir-casting technique. Alumina microballoons reinforced aluminum syntactic foam (AMRASF) has been developed using stir casting technique. Volume fraction of alumina microballoons in AMRASF varies in the range of 0.39–0.74. The compressive deformation behavior of these AMRASF is compared with that of cenosphere reinforced aluminum syntactic foam (CPRASF). The AMRASF does not exhibit clear plastic collapse stage as observed in case of CPRSAF. It is further noted that AMRASF shows the existence of work hardening phenomena after yielding but CPRASF does not show any significant work hardening after yielding even at higher relative densities of foam. This is explained on the basis of characteristics of alumina microballoons and cenospheres and interface characteristics between matrix and respective microballoons used. Effect of individual microballoons’ characteristics on the foam properties has also been explained.

A CFD Approach for Prediction of Unintended Porosities in Aluminum Syntactic Foam: A Preliminary Study

Aluminum Syntactic Foam (ASF) is a material with great potential in applications related to lightweight structures and structural damping. However, experimental investigations in literature report that the infiltration process to fabricate ASF often results in incomplete infiltration. Published studies on modeling the infiltration process are mainly based on a porous media/permeability approach. This approach focuses on the global porosity of ASF rather than local unintended porosity, since it does not include the infiltration pattern around the individual spherical particles. This paper reports a numerical approach that enables for the simulation of the flow through the porous corridors of the preform. The numerical approach is established in the commercial software FLOW-3D and consists of a finite volume based computational fluid dynamics solver and a volume of fluid algorithm which together calculates the pressure, velocity and free surface of the aluminum. The results of the numerical model illustrate that this method has great potential of predicting unintended porosities in ASF and thereby optimizing the parameters involved in the infiltration process.

Al–Al2O3 syntactic foams – Part I: Effect of matrix strength and hollow sphere size on the quasi-static properties of Al-A206/Al2O3 syntactic foams

The microstructure and quasi-static compressive mechanical properties of Al-A206/Al2O3 hollow sphere syntactic foams were investigated for foams with three different hollow sphere size ranges (0.106–0.212mm, 0.212–0.425mm, 0.425–0.500mm) and three different conditions including As cast (F), T4 and T7. The peak strength, plateau strength and toughness of the foams were found to increase with increasing wall thickness to diameter (t/D) ratio. Since the t/D ratio was found to increase with decreasing sphere diameter, the foams produced with the smallest hollow spheres (0.106–0.212mm) showed superior performance for the peak strength (F: 226MPa, T4: 312MPa, T7: 342MPa), plateau strength (F: 190MPa, T4: 269MPa, T7: 269MPa), and toughness (F: 59J/cm3, T4: 78J/cm3, T7: 88J/cm3). These properties were also found to generally increase with increasing matrix yield strength. The 0.212–0.425mm T7 heat treated syntactic foams in this study exhibit the highest specific plateau strength (102MPa-cm3/g) and the second highest specific energy absorption (41J/g) of aluminum syntactic foams reported in literature for which comparable data is available.

Compression and low-velocity impact behavior of aluminum syntactic foam

We report quasi-static compression and impact behavior of aluminum syntactic foams (ASF) produced by melt infiltration. Aluminum syntactic foams with relative density of 0.46 were produced using hollow alumina spheres (4.45mm and 3.05mm) randomly situated in a mold and two types of aluminum alloy (1100 and 6061). The impact behavior was investigated using an instrumented drop tower. We investigated the influence of the matrix alloy, the size of ceramic spheres, and the addition of a face sheet on the quasi-static compression and impact behavior of ASF. The 1100 Al ASF absorbed greater energy at higher velocities (penetration) than the 6061 Al alloy ASF, although at lower impact velocities, both ASF's absorbed the same amount of energy (equal-energy interval). The use of smaller microspheres did not increase the amount of energy absorbed compared to ASF's with larger microspheres and comparable relative density. The use of face sheets significantly increased the energy absorption capacity of the ASF's. Failure mechanisms are interpreted from impact load–displacement curves and examination of the impacted ASF plates. The properties of the ASF were compared to conventional aluminum foam and steel syntactic foams. The compression strength and energy absorption of the ASF were greater than that of conventional Al foams, but less than that of steel syntactic foam produced using the same hollow alumina spheres.

Microstructure and Compression Behavior of Cenosphere Filled Aluminum Syntactic Foams

Aluminum syntactic foams were fabricated by pressure-infiltrating liquid pure aluminum into packed preforms of cenosphere fly ash. The morphology, true density and porosity of fly ash microballoons were characterized. The microstructure of the syntactic foams demonstrated uniform distribution of the microballoons in the aluminum matrix and seldom infiltration of cenosphere fly ash. These foams were subjected to quasi-static uniaxial compression tests and behaved like high strength aluminum foams under compressive deformation, exhibiting an extended plateau region in the stress–strain curves. With the decreasing of fly ash diameter, the plateau stress and absorbed energy of the syntactic foams increased. X-ray microcomputed tomography was used to examine the foam microstructures after interrupted compression and reveal the damage evolution. The current work provides a better understanding on the structure and mechanical properties of aluminum matrix syntactic foams.

High temperature compressive deformation behaviour of aluminum syntactic foam

Abstract The high temperature compressive deformation behaviour of cenosphere filled aluminum syntactic foam has been studied at temperature between 100 °C and 200 °C and strain rate ranging from 10−3/s to 1/s. The plateau stress and densification strain are computed from stress–strain curve at various temperatures and strain rates. The plateau stress decreases with temperature irrespective of strain rate. Interestingly, plateau stress initially decreases with increase in strain rate and reaches to a minimum, and above a certain strain rate it starts increasing with strain rate irrespective of temperature. The densification strain remains invariant with strain rate but increases marginally with temperature. The strain rate sensitivity ‘m’ is found to be negative at a strain rate below the critical value and positive beyond the critical strain rate.

Sliding wear behaviour of aluminum syntactic foam: A comparison with Al–10 wt% SiC composites

The sliding wear behaviour of cenosphere-filled aluminum syntactic foam (ASF) has been studied in comparison with that of 10 wt% SiC particle reinforced aluminum matrix composite (AMC) at a load of 3 kg and varying sliding speeds under dry and lubricated conditions using a pin-on disc test apparatus. The tribological responses such as the wear rate, the coefficient of friction and the frictional heating were investigated. The wear surfaces and subsurfaces were studied for understanding the wear mechanism. It was noted that the coefficient of friction, the wear rate, and the temperature rise for ASF are less than that for AMC in both dry and lubricated conditions. The craters (vis-à-vis exposed cenospheres) play an important role in the wear mechanism for ASF.